In general, a knob, which has the same dictionary definition as a protruding handle, is a button that is configured to display or control a vehicle or an electronic product. Knobs may have various shapes, structures, and functions. For example, knobs are classified into a display type knob, such as a change knob of a transmission gear of a vehicle, a push type knob, such as a start button of a vehicle, or a rotary type knob, such as a volume adjustment knob of an audio system.
Conventionally, a synthetic resin was simply molded in order to manufacture the knob. In recent years, knobs having luxurious and aesthetically pleasing appearances have been proposed with increasing interest in the design of knobs. For example, a light emitting adjustment knob is disclosed in Korean Registered Patent Publication No. 10-1210906. As shown in FIGS. 1 and 2, a light emitting knob 1 includes a light blocking metal plate 10 having a light emitting display window 11 and a resin layer 20, made of a light-transmissive synthetic resin, coupled to the lower surface of the light blocking metal plate 10.
The resin layer 20 is coupled to the lower part of the light blocking metal plate 10 by bonding or by insert injection molding. In addition, referring to FIG. 2, a light emitting device 30 is installed under the resin layer 20 to display a predetermined message, such as “ENGINE START STOP,” outward through the light emitting display window 11 of the light blocking metal plate 10 in a light emitting fashion.
A method for manufacturing the conventional light emitting knob as described above will be described with reference to FIGS. 3 and 4. The method for manufacturing the conventional light emitting knob includes a metal plate processing step (S10) of processing a light blocking metal plate 10 such that the upper part of the light blocking metal plate is closed and the lower part of the light blocking metal plate is open, a resin layer coupling step (S20) of coupling a resin layer 20, which is made of a light-transmissive synthetic resin, to the inner side of the lower part of the light blocking metal plate 10, a display window forming step (S30) of forming a light emitting display window 11 in the upper surface of the light blocking metal plate 10 by carving, a surface treatment step (S40) of treating the upper surface of the light blocking metal plate 10, in which the light emitting display window 11 is formed, and a coating step (S50) of coating the treated upper surface of the light blocking metal plate 10.
In the method for manufacturing the conventional light emitting knob, as shown in FIG. 5, letters, such as E, N, G, I, N, S, and T, the start and the end of a cutoff line of each of which are attached to the light blocking metal plate 10, of “ENGINE START STOP,” which is the message, displayed through the light emitting display window 11, which is widely used, are not separated from the resin layer 20. However, the inner portions of letters, such as A, R, O, and P, which are separated from the light blocking metal plate 10 with the result that only the bottom surfaces of the letters are attached to the resin layer 20, i.e. “Δ” of A, “D” of R and P, and “O” of O, are easily separated from the resin layer 20 when light emitting display window 11 is formed by carving at the display window forming step (S30) and when the upper surface of the light blocking metal plate 10 is treated at the surface treatment step (S40), whereby a defect rate is increased.